Calculate the index of the first observation of each track based on an ID variable

Function to conveniently calculate the trackInd variable that is needed internally when fitting a model to longitudinal data with multiple tracks.

Usage

calc_trackInd(ID)

Arguments

ID

ID variable of track IDs that is of the same length as the data to be analysed

Value

A vector of indices of the first observation of each track which can be passed to the forward and forward_g to sum likelihood contributions of each track

Examples

uniqueID = c("Animal1", "Animal2", "Animal3")
ID = rep(uniqueID, c(100, 200, 300))
trackInd = calc_trackInd(ID)